1. Field of the Invention
Disclosed herein are an artificial ear and a method for detecting the direction of a sound source using the same.
2. Description of the Related Art
Recently, much interest has been focused on industries for intelligent robots that can interact with human beings. It is important that a robot detect the exact position of a robot user who is a conversational partner for Human-Robot Interaction (HRI). Therefore, a technique for detecting the direction of a sound source using an acoustic sensor is one of essential techniques for HRI.
The related art technique for detecting the direction of a sound source includes a method using Time Delay Of Arrivals (TDOA), a method using a Head-Related Transfer Function (HRTF) database of a robot platform, a beam-forming method using a plurality of microphone arrays, and the like.
The method using the TDOA is a method for estimating the direction of a sound source using a delay time at which a sound of a speaker arrives at each sensor. Since the method has a simple algorithm and a small amount of calculation, it is frequently used for estimating the position of a sound source in real time. However, when there is a constraint that a microphone should be disposed in a narrow area such as the position of each person's ear, i.e., when the distance between the microphones is shortened, the method is disadvantageous in that estimation resolution is reduced. When only two microphones are used in a narrow area, a sound source has the same delay time at two positions on a two-dimensional plane, and therefore, front-back confusion occurs. That is, if the position of a sound source is estimated based on only the delay time difference when only the two microphones are used, front-back discrimination is impossible.
The method using the HRTF is a method for detecting the direction of a sound source using information on the magnitude and phase of HRTFs. The method is similar to the sound source direction detecting method of human beings, but a change in transfer function, caused by an external ear, is shown in a frequency domain higher than the sound frequency area (˜4 kHz). Therefore, the method is disadvantageous in that a relatively large-sized artificial ear is needed and the amount of database for sound source direction detection is increased.
The beam-forming method is a method for matching a vector of a virtual sound source to a position vector of a real sound source while rotating the vector of the virtual sound source. In the beam-forming method, an array having a plurality of fixed sensors is necessarily used. When a plurality of microphones is used, a high-end hardware for signal processing is required, and the amount of data to be processed is increased. Therefore, the beam-forming method is disadvantageous in that it is unsuitable for detecting the direction of a sound source in real time.
In the related art techniques, the relative position between a sound source and a microphone is changed in real time. When the arrangement of microphones is restricted due to the shape of a robot platform, there is a limitation in applying the related art techniques.